Process

ABSTRACT

AN OXO PROCESS WHEREIN ANOLEFIN IS REACTED WITH HYDROGEN AND CARBON MONOXIDE IN THE PRESENCE OF A COBALT CARBONYL AND A TETRAALKYL OR A TETRAARYL DIPHOSPHINE, PREFERABLY IN THE PRESENCE OF A TRIALKYL AMINE.

United States Patent Olfice 3,560,572 Patented Feb. 2, 1971 3,560,572 PROCESS John F. Definer, Glenshaw, Edmond R. Tucci, Pittsburgh, and John V. Ward, Oakmont, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed Aug. 23, 1966, Ser. No. 574,320 Int. Cl. C07c 45/10 US. Cl. 260-604 Claims ABSTRACT OF THE DISCLOSURE An Oxo process wherein an olefin is reacted with hydrogen and carbon monoxide in the presence of a cobalt carbonyl and a tetraalkyl or a tetraaryl diphosphine, preferably in the presence of a trialkyl amine.

This invention relates to an Oxo process, or hydroformylation reaction, wherein hydrogen and carbon monoxide are added to an olefinic compound in the presence of a catalyst to obtain a mixture predominating in an aldehyde having one more carbon than said olefinic compound.

The catalyst generally employed for the h'ydroformylation reaction is a cobalt salt of a high molecular Weight fatty acid, such as octanoic, stearic, oleic, palmitic, Ilaphthenic, etc., acids. Inorganic salts, such as cobalt carbonate, can also be employed. Most of these salts are soluble in most of the olefinic feeds supplied to the hydroformylation reaction zone, but when they are not, they can be supplied in an inert, liquid solvent in which they are soluble, such as benzene, xylenes, naphtha, heptane, decane, dodecanol, etc. Although the catalyst is supplied in the form of a cobalt salt to the hydroformylation reaction zone, under the conditions existing therein the salt reacts with carbon monoxide, preferably in the presence of hydrogen, to form a cobalt carbonyl, that is, one or more of the following: cobalt hydrocarbonyl, HCo(CO) dicobalt octacarbonyl, Co (CO) and/or tetracobalt dodecacarbonyl, Co (CO) As defined herein cobalt carbonyl will refer to any one or all of the specific cobalt carbonyls referred to above. It is generally believed that the cobalt carbonyl is the active form of catalyst for the hydroformylation.reaction.

Since cobalt carbonyls are thermally unstable and will easily decompose to elemental cobalt and carbon monoxide, it is necessary to maintain a high pressure of hydrogen and carbon monoxide in the hydroformylation reaction zone to inhibit such decomposition at the elevated temperatures existing in the hydroformylation reaction zone. At the end of the reaction period, the reaction product will consist largely of an aldehyde having one carbon more than the olefinic charge, plus unreacted hydrogen and carbon monoxide and some alcohol, corresponding to the aldehyde, carrying dissolved cobalt carbonyl. The unreacted hydrogen and carbon monoxide can rather easily be separated from the reaction product, for example, by flash distillation, but the cobalt carbonyl is removed only with difficulty. It is obvious that if the aldehyde product, as such, is desired it would be necessary to remove cobalt carbonyl therefrom. In most cases the aldehyde is subjected to hydrogenation conditions in the presence of a hydrogenation catalyst, such as nickel, to convert the aldehyde to the corresponding alcohol. In such case, it becomes even more imperative to remove cobalt carbonyl from the aldehyde being hydrogenated, since at the lower pressures employed in the hydrogenation reactor cobalt carbonyl will decompose to cobalt and carbon monoxide, the latter being undesirable in the hydrogenation reaction zone, since it has a tendency to poison the hydrogenation catalyst, such as nickel, which is generally used.

It has been customary, therefore, to subject the hydroformylation reaction product to a decobalting operation to remove cobalt carbonyl therefrom. This has generally involved subjecting the hydroformylation reaction product to temperature and pressure conditions favoring the decomposition of cobalt carbonyl to elemental cobalt and carbon monoxide. Elemental cobalt is difficult to remove from the hydroformylation reaction product, and it has a tendency to plug the lines leading to and from the decobalter and for some to find its Way into the hydrogenation reactor. The removal of such cobalt adds significantly to the overall cost of the hydroformylation reaction. Cobalt so obtained, in addition, has to be discarded or, by a tedious procedure, may, perhaps, be converted back to the original cobalt salt or cobalt carbonyl for use in the hydroformylation reaction zone.

We have found, however, that the above difficulties can be avoided by employing in the hydroformylation reaction zone a cobalt catalyst, such as defined above, and a phosphine selected from the group consisting of tetraalkyl and tetraaryl diphosphines, including mixed alkylaryl diphosprines, having the following formula:

wherein R R R and R the same or different can be alkyl substituents having from one to 16 carbon atoms, preferably from one to 12 carbon atoms, or aryl. Specific examples of alkyl substituents are methyl, ethyl, n-propyl, nbutyl, n-pentyl, n-hexyl, n-hcptyl, noctyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, isopropyl, Z-methylbutyl, Z-ethylpentyl, 3-butylhexyl, 4-pentyldecyl, 2,2-dimethyldecyl, 3-methyl-4-ethyldecyl, S-propylhexyl, 3- methyldodecyl, 6-ethyldodecyl, 3,3-dimethyltetradecyl, 2- butylhexadecyl, etc., and of aryl substituents are phenyl, tolyl, xylyl, 1,3,5-trimethylphenyl, ethylphenyl, propylphenyl, butylphenyl, hexylphenyl, decylphenyl, dodecylphenyl, tetradecylphenyl, hexadecylphenyl, etc. Specific diphosphines that can be employed herein include tetra (methyl) diphosphine,

tetra (ethyl) diphosphine,

tetra (n-butyl) diphosphine,

tetra (n-hexyl) diphosphine,

tetra (n-decyl) diphosphine,

tetra (n-tetradecyl) dipho sphine,

tetra (n-hexadecyl) diphosphine,

tetra (phenyl diphosphine,

tetra (tolyl) diphosphine,

tri (ethyl) butyldiphosphine,

tri (n-butyl hexyldiphosphine,

tri (n-propyl methyldiphosphine,

tri (ethyl) tetradecyldiphosphine,

tri (n-pentyl hexadecyldiphosphine,

tri n-butyl) phenyldi hosphine,

tri (methyl isobutyldiphosphine,

tri (ethyl isoctyldiphosphine,

tri (ethyl 5-propylhexyldiphosphine, tri (methyl) 3-methyldecyldiphosphine, diethyldi (n-butyl) diphosphine, dimethyldiethyldiphosphine,

diethyldi (n-heptyl) diphosphine,

di (n-btuyl) di (isopropyl diphosphine, dimethyldi (n-dodecyl diphosphine,

di (isopropyl di isooctyl diphosphine, di (n-decyl) di (n-tetradecyl diphosphine, dimethyldi (n-heXadecyl) diphosphine, dimethyldiphenyldiphosphine, diethyldiphenyldiphosphine,

di (n-butyl) diphenyldiphosphine,

di (n-hexyl) diphenyldiphosphine,

di n-decyl) diphenyldiphosphine,

di (n-hexadecyldiphenyldiphosphine, diethylditolyldiphosphine,

di (n-butyl dixylyldiphosphine, dirnethyldicumyldiphosphine,

di isopropyl) di (6-ethyldodecyl) diphosphine, etc.

We believe that under the hydroformylation reaction conditions the tetraalkyl or tetraaryl phosphine, as a ligand, combines with the cobalt carbonyl and forms a complex therewith. By ligand we intend to include a tetraalkyl or tetraaryl diphosphine which contains an element with an electron pair that can form a coordination compound with a metal compound. While we are not absolutely certain, we have reasons to conclude that the complex formed between cobalt carbonyl and the above defined diphosphine can be expressed by the following structural formula:

wherein R R R and R the same or different, are alkyl or aryl substituents, as defined above, x is a whole number from 2 to 3 and y is a whole number from 1 to 2. Although the complex defined above is thermally stable and can be used, as such, in a number of hydroformylation reactions without appreciable decomposition thereof, the complex can be rendered even more thermally stable by employing in admixture therewith a selected amount of a trialkyl amine having a pK acidity of at least about +8 but no greater than +15, preferably a pK acidity of about +10 to about +13. By pK acidity we mean to refer to the negative logarithm of the Bronsted acid dissociation constant. Weak bases have low pK values, while strong bases have high pK values. Although there may be some tendency for the trialkyl amine to complex with the cobalt carbonyl, we are of the opinion that only a small amount of such complexing takes place, since there is a greater tendency for a complex to form between cobalt carbonyl and the diphosphine defined above. To the extent that a complex forms between cobalt carbonyl and the above amine, the same can be defined in accordance with the following structural formula:

wherein x is a whole number from one to four, y is a whole number from one to four, x+y= and R is an alkyl substituent of the amine as defined below.

By trialkyl amines we intend to include those trialkyl amines whose individual alkyl substituents will have from one to 16 carbon atoms, preferably from about one to 12 carbon atoms, as well as those whose alkyl substituents carry one or more aldehydic, alcoholic, chlorine, fluorine, naphthyl or phenyl substituents thereon. Each of the individual alkyl substituents attached to the nitrogen atom of the amine, moreover, does not have to be similar to another substituent on the same amine. Specific amines that can be employed herein include trimethylamine, tri-n-butylamine, tri-n-hexylamine, tri-n-dodecylamine, tri-n-hexadecylamine, tribenzylamine, N,N-dimethylbenzylamine, N,N-dimethylnaphthylamine, N,N-methylbutylbenzylamine, N,N-butylethylbenzylamine, N,N-diethyldodecylamine, 2,2,2"-iminotriethanol, 2,2',2"-iminotriethylchloride, 4,4,4"-iminotributylchloride, 1,1',1"-irninotrimethylfiuoride, 4,4,4"-iminotributyraldehye, 7,7,7"-iminotriheptaldehyde, etc.

The cobalt complex defined above, that is, the complex formed between cobalt carbonyl and the diphosphine, is easily obtained and employed herein. In the preferred embodiment it is obtained in situ in the hydroformylation reaction zone. Thus, one of the cobalt salts, for example, one of those defined above is introduced into the hydroformylation reaction zone along with one of the defined diphosphines, the olefin to be subjected to hydroformylation reaction, hydrogen and carbon monoxide. Any olefinic compound that can be subjected to hydroformylation reaction and can be converted therein to aldehyde having one more carbon than said olefin can be employed.

Representative examples of olefins that can be employed include propylene, butene-l, pentene-l, hexene-l, heptene- 1, octene-l, decene-l, tetradecene-l, hexadecene-l, 2-pentene, 2-hexene, 2-heptene, 2-octene, 4-methy1-1-pentene, 2,4,4-trimethyl-l-pentene, 4-methyl-2-pentene, 2,6-dimethyl-3-heptene, cyclopentene, cycloheptene, cyclooctenc, 4- methyl-l-cyclohexene, etc. The molar ratio of hydrogen to carbon monoxide can be from about 5:1 to about 0.5:1, preferably about 1:1 to about 2:1. The amount of hydrogen and carbon monoxide needed is at least that amount stoichiometrically required for addition to the olefinic compound, although from about 1 /2 to about three times the amount stoichiometrically required can be employed. The amount of diphosphine employed is from about 0.5 to about 10, preferably from about one to about four mols per mol of cobalt carbonyl. When an amine is employed it is also introduced into the reaction zone. From about 0.5 to about 10, preferably from about two to about four mols of amine per mol of cobalt carbonyl can be employed.

The reaction conditions in the hydroformylation reaction zone can vary over a wide range. Thus the temperature can be from about 150 to about 475 F., preferably from about 250 to about 400 F., while the pressure can be from about 500 to 5000 pounds per square inch gauge, preferably from about 1000 to about 3000 pounds per square inch gauge. Reaction time can be from about five minutes to about five hours, but preferably will be from about 30 minutes to 120 minutes.

As a result of the above the cobalt salt will be converted to cobalt carbonyl and the latter, in turn, will complex with the diphosphine to form the new complex defined above, which becomes the hydroformylation reaction catalyst. At the end of the reaction period the converted product obtained will contain from about 50 to about percent by weight of aldehyde having one more carbon than said olefinic charge and from about two to about 40 percent by weight of alcohol corresponding to said aldehyde. Also present with the converted product, of course, are unreacted hydrogen and carbon monoxide but also the cobalt carbonyl diphosphine complex and the trialkyl amine, when the latter is also employed. The unreacted hydrogen and carbon monoxide can be recovered from the reaction product in any convenient manner, for example, by flashing at a temperature of about 25 to about 100 C. and a pressure of about 15 to about 500 pounds per square inch gauge. The aldehyde and alcohol present in the resulting reaction product can be removed therefrom in any convenient manner, for example, by subjecting the resulting reaction mixture to a temperature of about 30 to about 200 C. and a pressure of about 0.001 to about 760 mm. absolute pressure. As a result of such action the aldehyde and alcohol are flashed off together or separately and left behind is the cobalt catalyst complex, trialkyl amine and/ or solvent, when used and a small amount of polymerization product, which can be primarily acetals, hemiacetals and esters. A feature of the present process is that less polymer is formed herein than is generally formed during the conventional hydroformylation reaction process wherein uncomplexed cobalt carbonyl is employed as catalyst. Another additional, and quite important feature of the present process, is that the ratio of normal aldehyde and/or normal alcohol to iso aldehyde and/or iso alcohol is very high, from about 4:1 to about 1121. Normal aldehydes and/ or normal alcohols are highly desirable commercially. Thus, normal aldehydes can be aldolized to yield Z-ethylhexanol which is useful as a plasticizer, or they can be hydrogenated to normal alcohols which are useful as commercial solvents or plasticizers. The cobalt carbonyl complex herein, along with the trialkyl amine, when used, can be recovered from the polymer in any convenient manner, for example, by ion exchange, solvent extraction or distillation, or can be permitted to remain in combination with the polymer, which can serve as solvent therefor, and can be reused during the hydroformylation reaction as previously defined. This procedure can be repeated many times, since the cobalt carbonyl complex defined herein is stable and will not decompose under the reaction and recovery conditions employed herein.

The cobalt carbonyl complex catalyst need not be formed in situ, as defined above, but can be preformed. Thus a mixture of cobalt carbonyl, such as defined above, can be combined with one of the diphosphines, preferably in an inert solvent such as benzene, xylene, naphtha, heptane, decane, etc., at a temperature of about 3 to about 250 C., preferably about 25 to about 150 C., and a pressure of about 15 to about 5000 pounds per square inch gauge, preferably about 15 to about 100 pounds per square inch gauge for about one to about 120 minutes, preferably for about to about 30 minutes. If an amine is to be used in combination with the complex so formed it can be added to the mixture along with the diphosphines, or it can be added to the complex in the hydroformylation reaction zone. If desired, the cobalt carbonyl complex can be obtained as defined immediately above by substituting one of the previously defined cobalt salts for the cobalt carbonyl. In such case, however, at least about one to about 20 mols of carbon monoxide,

ture in any suitable manner, for example, by ion exchange, solvent extraction or distillation.

The process of this invention can further be illustrated by the following:

EXAMPLE I A series of runs were made wherein olefins were subjected to hydroformylation reaction in the presence of the cobalt carbonyl complex defined above. Thus, into a 500 milliliter stainless steel autoclave there was placed 100 milliliters of benzene and 11 grams of a solution containing eight milliliters of benzene and four grams of the cobalt salt of 2-ethylhexanoic acid. The autoclave was flushed with nitrogen gas and then pressured with synthesis gas containing 1.2 mols of hydrogen per mol of carbon monoxide to a pressure of 300 pounds per square inch gauge. The autoclave was depressured to atmospheric pressure and repressured with synthesis gas several times. The autoclave was finally pressured with synthesis gas to about 2300 pounds per square inch gauge at room ternperature ,and then heated to 350 F. within to minutes. A temperature of 350 F. and a pressure of 3500 pounds were maintained for one hour. The autoclave was cooled to F. and thereafter slowly depressured to atmospheric pressure.

To the dicobalt octacarbonyl thus formed in the autoclave there was added diphosphine to be complexed therewith, a trialkyl amine when used, and hydrogen and carbon monoxide in a molar ratio of 1.2:1 and the olefin. The reaction mixture was maintained at hydroformylation reaction temperature and pressure for one hour to obtain a reaction product containing substantial amounts of an aldehyde having one more carbon than the reactant olefin and the corresponding alcohol. At the end of the reaction period the autoclave was cooled to about 75 F. and then depressured to atmospheric pressure and the product analyzed for its composition. The results obtained are tabulated below in Tables I and II.

TABLE I Run Number Temperature, F 250 320 350 0 350 320 320 320 320 Pressure, pounds per square in. guage 1, 000 1, 000 1, 000 1, 000 1, 000 1, 000 1, 000 1, 000 500 Residence time, minutes- 60 60 60 60 60 60 60 60 6O C0 (CO) ,,gra;ms 2. 0 2.0 2. 0 2. 0 2.0 2. 0 2.0 2.0 2. 0 Tetrabutyldiphosphine, gram 4.0 4.0 4. 0 4. 0 4. 0 6. 0 4. 0 2. 0 2. 0 Tri-n-butylamine, grams None None None 3. 9 3. 9 3. 9 3. 9 3.9 3. 9 Propylene, grams 8. 8. 0 8. 0 8. 0 8. 0 8. 0 8. 0 8. 0 8. 0 Benzene, grams 78 78 78 78 78 78 78 78 Selectivity to normal product, percent 82. 9 87. 0 86. 3 91.4 88. 7 87. 9 87. 0 79. 0 88. 4 Conversion, percent 5. 1 81. 2 73. 3 70.0 97. 3 80. 2 81.9 86. 4 60. 0

TABLE II Run Number Temperature, F 290 310 320 320 320 320 290 290 320 320 Pressure, pounds per square in ua e 3, 500 1, 000 1, 000 1, 000 1, 000 1, 000 3, 500 1, 000 1, 000 1,000 Residence time, minutes 0 60 60 60 6O 60 60 0 60 C02(CO)a, grams 2. 0 2. 0 2. 0 4.0 2.0 2.0 2.0 2. 0 2. 0 2. 0 Dipliosphine, grams- 4. 0 4. 0 1 4.0 8.0 2 4.0 2 4.0 2 4.0 2 4.0 a 4. 0 5 6. 0 Amine,grams 3. 4.5 4.5 7.8 4.5 3.9 3.9 3.9 3.9 3.9 Olefin,grams 60.0 8.0 20.0 8.0 20.0 8.0 8.0 8.0 8.0 8.0 Benzene, grams 78 78 78 78 78 78 78 78 78 78 Selectivity to normal product, percent. 90. 2 88. 4 87.3 87.8 87. 0 86 4 89.7 89. 4 85. 6 86.8 Conversion, percent 23. 2 67. 9 36. 5 86. 4 65. 0 72 1 14. 9 18. 4 89. 5 78. 3

1 Tetrabutyldiamine. 2 Tetraethyldiphosphine.

3 Diphenyldibutyldiphosphine.

4 Tri-n-butylamme.

5 N,N-dimethylbenzylamine. 6 Tri-heptylamine.

Propylene.

B Hexene-l.

preferably about one to about eight mols of carbon monoxide, relative to the cobalt salt must also be present.

The resulting mixture can be used as such in the hydro-- formylation reaction zone as catalyst, or if desired the cobalt carbonyl complex can be recovered from the mix- 75 in the appended claims.

P--P Ra wherein R R R and R are selected from the group consisting of alkyl groups and aryl groups.

2. The process of claim 1 wherein R R R and R are alkyl groups.

3. The process of claim 1 wherein R R R and R are aryl groups.

4. The process of claim 1 wherein said diphosphine is tetrabutyldiphosphine.

5. The process of claim 1 wherein said diphosphine is tetraethyldiphosphine.

6. The process of claim 1 wherein said diphosphine is diphenyldibutyldiphosphine.

7. The process of claim 1 wherein the reaction is carried out in the additional presence of a trialkyl amine having from one to sixteen carbon atoms.

8. The process of claim 1 wherein the reaction is carried out in the additional presence of a trialkyl amine having a pK acidity of 8 to 15.

9. The process of claim 1 wherein the reaction is carried out in the additional presence of tri-n-butyl amine.

10. The process of claim 1 wherein the reaction is carried out in the additional presence of N,N-dimethyl benzylamine.

11. The process of claim 1 wherein the reaction is carried out in the additional presence of tri-n-heptyl amine.

12. The process of claim 1 wherein the hydroformylation reaction temperature is from about 150 to about 475 F. and pressure is from about 50 to about 5000 pounds per square inch gauge.

13. The process of claim 1 'wherein the olefin is propylene.

14. The process of claim 1 wherein said catalyst is recovered and reused in a subsequent hydroformylation reaction.

15. The process of claim 1 wherein the cobalt carbonyl is dicobalt octacarbonyl.

References Cited UNITED STATES PATENTS 3,401,204 10/1968 Mason et al. 260-6l7X 3,278,612 10/1966 Greene 260-604X 3,239,569 3/ 1966 Slaugh et al. 260-604 LEON ZITVER, Primary Examiner R. H. LILES, Assistant Examiner US. Cl. X.R.

@2 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,560, 572 ed February 2, 1971 Patent No.

Inventor) John F. Deffner, Edmond R. 'lucci, John V. Ward It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, TABLE II, in the list of notes,

" l Tetralbutyldiphosphim "1 Tetrabutyldiamine" should read Column 8, claim 12, line 3, please change "50" to "500".

Signed and sealed this 18th day of May 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR.

Commissioner of Patents Attesting Officer 

